Conventional idler pulleys for power transmission require either substitution or shifting of the transmission belt or chain. In the case of step pulleys, when a change of speed is desired, it is necessary to put a pulley of different diameter into operation. Especially in multiple pulley transmission installations, this requirement can be a laborious time-consuming chore.
Additionally, idler pulleys now in use have inadequate flexibility for maintaining optimum tension on the belts or chains which they carry. Constant attention and adjustments are necessary to prevent excess belt slackness caused by stretching, and to avoid wear and power loss.
The best of the prior art idler pulleys have some adjustability provided by spring-biased moveable flanges, which adjust to relatively small speed changes by carrying their transmission belts higher or lower on the sloped inner flange surface. Typical of this type are variable speed belt drives produced by Lovejoy, Inc. of 2655 Wisconsin Avenue, Downers Grove, Ill. 60515. However, the speed change range on these presently available pulleys is small, and optimum constant tension for uniform operations is difficult to maintain.
It is therefore a primary object of this invention to provide an idler pulley which is self-adjusting to a wide range of transmission speed variation.
Another object of this invention is to provide an idler pulley which automatically adjusts to minor variations in the length of the power transmission belt or chain it carries and maintains an even tension.
Still another object of the invention is to provide a self-adjusting idler pulley which is simple in design and inexpensive to produce.